1. Field of the Invention
The present invention relates to a semiconductor device having a chip which has a pad, a bump electrode formed on the pad, and a wire whose stitch bonding is performed on the bump electrode, and its manufacturing method.
2. Background Art
When performing stitch bonding of a gold wire on an aluminum pad on a chip directly, load of a capillary concentrates and a crack enters into SiO2 interlayer insulation film under the aluminum pad. For this reason, a bump electrode is used for the wire bonding between a chip and a chip (chip-to-chip) (for example, refer to Japanese Unexamined Patent Publication No. 2001-15541). Further, in a thin package, in order to make the height of a gold wire low, reverse bonding using a bump electrode is performed.
FIGS. 10A and 10B are sectional views showing the state of conventional bump electrode formation. First, as shown in FIG. 10A, bump electrode 14 is formed on aluminum pad 11 of a chip with gold wire 13 discharged from capillary 12. Then, as shown in FIG. 10B, gold wire 13 is cut by pulling upward, while holding both sides of gold wire 13 by clamper 15.
FIGS. 11A and 11B are sectional views showing the state of conventional stitch bonding of a gold wire onto a bump electrode. First, as shown in FIG. 11A, gold wire 13 is crushed by pushing and pressing gold wire 13 to bump electrode 14 and applying supersonic vibration by capillary 12, and gold wire 13 is joined to bump electrode 14. Then, as shown in FIG. 11B, gold wire 13 is cut by pulling upward, while holding both sides of gold wire 13 by clamper 15.
However, since the gold wire used as a material of bump electrode 14 is soft in the conventional formation of a bump electrode with a gold wire and conventional stitch bonding of a gold wire onto a bump electrode, crush of gold wire 13 held by capillary 12 and bump electrode 14 becomes insufficient, so that gold wire 13 cannot become sufficiently thin. Hereby, since the strength of gold wire 13 becomes high, the distortion of gold wire 13 by the reaction at the time of cutting gold wire 13, and the peeling of bump electrode 14 from aluminum pad 11 occur. The same phenomenon is generated also in the conventional bump electrode formation. As a result, there was a problem of gold wires having electrically short-circuited with S character deflection of gold wire 13 resulting from distortion, and opening electrically by peeling of bump electrode 14.
What is necessary is just to use the soft type gold wire cut by lower load, in order to solve this problem. However, since the modulus of elasticity is low, the such soft type gold wire had the problem that a gold wire flowed when sealing resin was poured, and gold wires electrically short-circuited.